Download A Comparison of the Acute Hemodynamic Effects of Inhaled

Original
Article
A Comparison of the Acute Hemodynamic Effects
of Inhaled Nitroglycerin and Iloprost in Patients
with Pulmonary Hypertension Undergoing
Mitral Valve Surgery
Nurgul Yurtseven, MD,1 Pelin Karaca, MD,2 Gunseli Uysal, MD,1 Vedat Özkul, MD,1
Serdar Cimen, MD,3 Abdullah Kemal Tuygun, MD,3 Adnan Yuksek, MD,1
and Sevim Canik, MD1
Background: Since the presence of pulmonary hypertension (PHT) affects the prognosis of the
patients, it is important to manage and evaluate PHT. The aim of this study was to compare the
hemodynamic effects of inhaled nitroglycerin and iloprost during early postoperative period, in
patients with PHT undergoing mitral valve replacement surgery.
Materials and Methods: One hundred patients with PHT (mean pulmonary artery pressure
(MPAP) >25 mmHg at rest), were randomized to receive either inhalation of nitroglycerin (group
I; n=50) or iloprost (group II; n=50) in the postoperative period. In both groups, baseline hemodynamic parameters were recorded before the treatment (T0). Then, patients in group I received
20 애g.kg −1 nitroglycerin and those in group II received 2.5 애g.kg−1 iloprost. The same parameters were recorded immediately after the end of the treatment (T1).
Results: In both study groups MPAP and pulmonary vascular resistance (PVR) were found to
be significantly lower at T1 when compared to that of T0 period (p<0.05). MPAP and PVR were
significantly lower and mean arterial pressure (MAP) was significantly higher in group II when
compared to group I at T1 period (p<0.05). In addition to decreases in PVR and MPAP, iloprost
also increased cardiac output (CO)(4.9앧1.3 vs 5.1앧0.9, p<0.05) and stroke volume (SV)(48앧13
vs 56앧13, p<0.05).
Conclusion: Inhaled iloprost and nitroglycerin, both effectively reduce MPAP and PVR without affecting MAP, systemic vascular resistance (SVR) and CO. However, iloprost seems to be a
more powerful pulmonary vasodilator, therefore we suggest iloprost inhalation in patients with
severe PHT. (Ann Thorac Cardiovasc Surg 2006; 12: 319–23)
Key words: pulmonary hypertension, iloprost, nitroglycerin
Introduction
Pulmonary hypertension (PHT) is a clinical entity, that is
From the Departments of 1Anesthesiology and Reanimation, and
3
Cardiovascular Surgery, Dr. Siyami Ersek Thoracic and Cardiovascular
Surgery Hospital, and 2the Department of Anesthesiology and
Reanimation, Anadolu Health Care, Istanbul, Turkey
Received January 10, 2006; accepted for publication April 3, 2006.
Address reprint requests to Pelin Karaca, MD: the Department of
Anesthesiology and Reanimation, Anadolu Health Care, Postane Mah.
Rauf Orbay Cad., Bilginoǧlu Sitesi NO 4 Tuzla, Istanbul, Turkey.
Ann Thorac Cardiovasc Surg Vol. 12, No. 5 (2006)
frequently seen in patients with mitral valve disease.
Unfortunately, elevated pulmonary artery pressure (PAP)
might persist after mitral valve replacement in the early
postoperative period.1)
Elevated PAP and/or pulmonary vascular resistance
(PVR), increases the risk of development of acute right
heart failure. Thus, strict control of PAP is an essential part
of the postoperative care of this subset of patients.2–4) Although parenteral vasodilators are theoretically beneficial, they have been used with limited clinical results because of the lack of pulmonary selectivity. Therefore, in
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Yurtseven et al.
recent years inhaled nitric oxide, nitroglycerin and
prostacyclin (PGI2) analogues become popular.2,5,6) In our
previous study we have shown that inhaled nitroglycerin
decreases PAP and PVR without affecting systemic arterial pressure in patients with PHT undergoing mitral valve
replacement surgery.7) The present study aims to compare the effects of inhaled iloprost, a synthetic prostacyclin
analogue, and inhaled nitroglycerin again in this subset
of patients.
Materials and Methods
After obtaining ethic committee approval and informed
consent, 100 patients with PHT (having mean PAP
(MPAP) >25 mmHg) were randomized to receive either
inhalation of nitroglycerin (group I; n=50) or iloprost
(group II; n=50) in the postoperative period. Exclusion
criteria were a history of chronic obstructive pulmonary
disease and left ventricular ejection fraction <40%.
Anesthesia was induced with intravenous fentanyl (20
애g.kg−1) and propofol (2 mg.kg−1). Muscle relaxation was
provided with pancuronium (0.1 mg.kg−1). Anesthetic
maintenance was ensured with fentanyl infusion 0.3–1.0
애g.kg−1.min−1, propofol (1 mg.kg−1), and isoflurane (0.4–
1.0%). During the first 8 postoperative hours patients were
sedated with fentanyl 2 애g.kg−1h−1 and the study was continued. They were ventilated with 40% oxygen. Tidal
volume was set at 10 ml.kg−1, respiratory rate was adjusted to establish an arterial carbon dioxide tension and
arterial pH approximately 35 mmHg and 7.40, respectively.
The measured hemodynamic parameters were heart
rate (HR), mean arterial pressure (MAP), MPAP, central venous pressure (CVP), and pulmonary capillary
wedge pressure (PCWP). Parameters derived by standard formulas include cardiac output (CO), pulmonary
vascular resistance (PVR) and systemic vascular resistance (SVR). CO was measured using a 7-F thermodilution pulmonary artery catheter during expiration. In
both groups, baseline hemodynamic parameters were
recorded before the treatment (T0), upon arrival to the
surgical intensive care unit (SICU). Then, patients in
group I and group II, inhaled 20 애g.kg−1 nitroglycerin,
and 2.5 애g.kg−1 iloprost liquid, nebulised by 2 L.min−1
air jet, from the inspiratory limb of the ventilator. The
previous measurements were repeated at the end of the
treatment (T1).
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Statistical Analysis
Statistical procedures were done by using statistical software package (STATISTICATM 6.0, StatSoft Inc., USA).
Statistical power analysis using 움=0.05 and 웁=0.2 indicated that a total of 50 observations would be needed to
detect a difference between groups with an assumed standard deviation (SD) of 10 with the power of 80%. Data
are expressed as mean앐SD. The variables were analysed
with Student-t test. P<0.05 was considered to indicate
statistical significance.
Results
Between January 2004 and November 2005, 100 patients
with PHT undergoing mitral valve replacement surgery
were prospectively enrolled. Patient characteristics are
presented in Table 1. There were no statistically significant differences between the study groups. All patients
tolerated iloprost and nitroglycerin inhalation without side
effects.
The hemodynamic parameters are illustrated in Table 2.
There were no significant differences between the study
groups with respect to baseline hemodynamic characteristics (T0). In both study groups MPAP and PVR significantly decreased after treatment (T1) as compared with
baseline (T0)(p<0.05). Whereas, MPAP, PVR and CVP
were significantly lower in group II when compared to
group I at T1 period (p<0.05). Iloprost inhalation reduced
PVR (289앐136 vs 124앐57 dyn.sec −1.cm−5, p<0.05),
MPAP (36앐6 vs 19.5앐4 mmHg, p<0.05) and CVP (10앐3
vs 8앐3 mmHg, p<0.05) (Figs. 1 and 2). In addition to
decreases in PVR and MPAP, iloprost also increased CO
(4.9앐1.3 vs 5.1앐0.9, p<0.05) and stroke volume (SV)
(48앐13 vs 56앐13, p<0.05).
Discussion
Although the quantity of blood flowing through the lungs
is essentially equal to that flowing through the systemic
circulation, the pressures in the pulmonary circulation are
significantly low compared to the systemic circulation.
Thus, pulmonary circuit is a low-resistance system. The
smooth muscle cells in the pulmonary vessel walls, by
reacting the substances released from the endothelium,
not only keep the pulmonary vascular tree compliant, but
also diverge the blood flow to those segments of the lungs
where the alveoli are best oxygenated. Vascular endothelium contributes this regulation by releasing a number of
Ann Thorac Cardiovasc Surg Vol. 12, No. 5 (2006)
Acute Hemodynamic Effects of Inhaled Nitroglycerin and Iloprost in Pulmonary Hypertensive Patients
Table 1. Patient characteristics
Parameters
Nitroglycerin
Iloprost
p value
Age (years)
Sex (M/F)
Weight (kg)
Height (mt)
49.2앐9.7
22/28
63.3앐10.7
1.61앐5.9
53.8앐11.7
21/29
70.7앐12.4
1.65앐6.07
ns
ns
ns
ns
M, male; F, female; ns, not significant.
Table 2. Hemodynamic parameters
Variables
-1
HR (min )
CO (L.min-1)
SVR (dyn.sec-1.cm-5)
PVR (dyn.sec-1.cm-5)
SV (ml.beat-1)
MAP (mmHg)
MPAP (mmHg)
CVP (mmHg)
PCWP (mmHg)
Nitroglycerin
98앐11
5.0앐1.3
1,468앐377
286앐192
49앐14
72앐8
37앐10
9앐5
19앐7
Iloprost
T1
T0
T0
95앐13
4.9앐0.9
1,294앐345
162앐59.6*
50앐11
66앐9
24.5앐4*
8앐4
15앐9
96앐11
4.9앐1.3
1,340앐496
289앐136
48앐13
70앐12
36앐6
10앐3
20앐5
T1
98앐12
5.1앐0.9*†
1,145앐374
124앐57*†
56앐13*†
68앐11
19.5앐4*†
8앐3*†
16앐8
Effects of inhaled nitroglycerin and iloprost in heart rate.
Data are expressed as mean앐SD.
*, p<0.05 versus baseline; †, p<0.05 versus nitroglycerin group.
HR, heart rate; CO, cardiac output; SVR, systemic vascular resistance; PVR, pulmonary vascular
resistance; SV, stroke volume; MAP, mean arterial blood pressure; MPAP, mean pulmonary arterial
pressure; CVP, central venous pressure; PCWP, pulmonary capillary wedge pressure.
vasoactive substances.8)
PHT is a pathophysiologic state that can be primary or
associated with many other clinical conditions. It is common in patients with long-standing cardiac valvular pathology. At least three pathophysiologic mechanisms contribute to the PHT seen in this subgroup of patients. These
include; increased left atrial pressure transmitted retrograde into the pulmonary circulation. Vascular remodelling of the pulmonary vasculature in response to chronic
obstruction to pulmonary venous drainage (fix component) and pulmonary arterial vasoconstriction (reactive
component). PHT is usually a reflex originating during
the immediate period. However, over time other morphologic changes take place. In these cases the treatment of
PHT is represented by the treatment of the underlying
pathology.9)
The treatment of mitral valvular disease is usually mechanical and necessitates the use of extracorporeal circulation. In addition, cardiopulmonary bypass (CPB) might
contribute to the increased MPAP and therefore increase
the work-load of the right ventricle in this group of pa-
Ann Thorac Cardiovasc Surg Vol. 12, No. 5 (2006)
tients. Several days even weeks might be required for the
increased PVR to return to normal after the valve replacement.10,11) During this critical period it is important to keep
PVR within the limits against which the right ventricle
can work. Thus, patients undergoing valve surgery might
require pulmonary vasodilator therapy during the immediate postoperative period.12) The main limitation of systemic vasodilator therapy is accompanying systemic hypotension. The long-term use of calcium-channel blockers
decreases the PAP and PVR. Approximately 25% of patients can tolerate this treatment.13,14) Intravenous administration of nitroglycerin and PGI2 was shown to improve
hemodynamic variables. However, the lack of pulmonary
selectivity and the occurrence of tolerance limits the usefulness of these vasodilators.8,15) These shortcomings
neccessiate the search for the new agents and techniques
to decrease adverse effects. During the last decade research has been directed towards inhaled nitric oxide
(INO). INO was shown to be effective in the treatment of
PHT, but it is expensive and toxic side effects limit its
use.16) On the other hand, nitroglycerin is metabolized to
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dyn.sec.cm−5
mmHg
Yurtseven et al.
Fig. 1. SVR and PVR changes.
SVR, systemic vascular resistance; PVR, pulmonary vascular
resistance; ntg, nitroglycerin; ilo, iloprost.
Fig. 2. MAP and MPAP changes.
MAP, mean arterial pressure; MPAP, mean pulmonary artery
pressure; ntg, nitroglycerin; ilo, iloprost.
nitric oxide which is a potent vascular smooth muscle
relaxant in the vascular endothelial cells.1) We recently
showed that inhalation of nitroglycerin decreases PAP
without affecting systemic blood pressure in the early
postoperative period in patients who underwent mitral
valve replacement surgery. Our results were consistent
with previous findings published by Gong et al.,17) in dogs
with experimentally induced PHT and Omar et al.18) in
patients with PHT resulting from congenital cardiac defects. In this study we extended these findings to compare the effects of two agents; nitroglycerin and iloprost,
the stable analogue of PGI2.
This study corroborates our previous findings that inhaled nitroglycerin reduces MPAP and PVR without affecting MAP, SVR, and CO.7) However, inhalation of aerosolized iloprost seems to be a more effective approach
considering the results of the two groups; MPAP and PVR
were significantly lower and MAP, SV and CO were significantly higher in group II when compared to group I at
the T1 period. In addition, although not statistically significant, iloprost caused a decrease in PCWP. These findings suggest that inhaled iloprost selectively targets the
pulmonary vasculature.
Theodoraki et al. reported that a selective pulmonary
vasorelaxation was achieved by iloprost in cardiac surgery patients who presented with severe RV dysfunction
following discontinuation of CPB.2) After iloprost inhalation, MPAP and PVR decreased with no change in MAP
and SVR.2) Their results compare favorably with our findings.
Sablotzki et al. studied the effects of inhaled aerosolized
iloprost in patients with PHT due to chronic cardiac failure.19) They found that iloprost caused a significant reduction in MPAP and PVR with no effects on SVR and
arterial blood pressure. In comparison to the results of
Sablotzki et al. we found similar effects of iloprost both
on pulmonary and systemic circulation.19)
Inhaled PGI2 was shown to be a more potent pulmonary vasodilator than INO in several studies. 20,21)
Olschewski et al. tested the short-term effects of INO,
PGI2, and iloprost and found that INO-evoked decrease
in PVR was less than that seen in response to inhaled
iloprost and PGI2.12) Hoeper et al. reported more potent
effects of inhaled iloprost on the pulmonary vascular bed
as compared to INO in patients with primary PHT.22) Our
results are parallel to that of Hoeper et al. 22) and
Olschewski et al.,21) the decrease in MPAP and PVR was
more pronounced in iloprost group and associated with
an increase in CI, SV and MAP.
In our study, inhaled iloprost was well tolerated. The
side effects, such as, jaw pain, syncope and flushing were
seen in no patients.
Overall, our data support the conclusion that aerosolized iloprost caused marked pulmonary vasodilatation
and increase in CI and MAP. Thus, it appeared to be an
effective and safe treatment in patients with PHT after
mitral valve replacement.
322
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